Sir John described Russia as always having been an "issue of concern" for security services.

"Europe and Russia are not converging with one another so we're going to have to find a new way to coexist with Russia," he said.

"This crisis at the moment - it's focused on Ukraine but Ukraine is a symptom. It's not the real problem.

"The real problem is how we live with a Russia which feels very exposed. Putin's actions are ones of a leader who believes his own security is at stake.

"And here we've got nuclear bombers approaching the Cornish coast."

Jihadist threat

Sir John said the UK needed to prepare to take defensive measures for itself and the nation's allies, which include the Baltic states and central Europe.

"We've got to have the capability to deal with things like the hybrid warfare that we've seen Russia deploy, first in Crimea and then in the Donbass region, we've got to have the ability to deal with cyberwarfare.

"What's really important is that we're able to fulfil all of our defence commitments and I think that that's going to require a reversal in the trend in defence spending.

"We're going to have to spend more on our defence and our security because the threats are greater."

In a wide-ranging interview, Sir John also discussed the threat from jihadists.

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His comments come after Mohammed Emwazi, a Kuwaiti-born British man in his mid-20s and from west London, was identified as "Jihadi John", an individual pictured in the videos of several beheadings of Western hostages.

Sir John said there were two answers to the question of why people became radicalised.

The first is that Muslims "are less well integrated" into UK society "and there are a number of social and economic factors that are related to that".

Secondly, he said, the Islamic religion "as a whole is not well geared to reviving and modernising itself so that it meets the values and the norms of a 21st Century society".

"So there's a big political challenge which can only really be taken up by leaders in the Islamic world... it can't be imposed by the West."